1. Field of the Invention
This invention relates to a color smear correcting apparatus wherein, for a video signal of parent and son pictures input from a frame sequential imaging apparatus, the color smear of the parent picture and the color smear of the son picture are corrected independently.
2. Description of Related Art
There exists in the prior art an optical endoscope wherein an illuminating light emitting means is built-in on the tip side of an elongate insertable part, and an imaging means for imaging an object image illuminated by the illuminating light emitting means is also built-in.
Also, recently, there is practiced an electronic endoscope is known wherein such solid state imaging device as a CCD is built-in on the tip side of an insertable part so that an object image may be color-displayed in a display and may be easily recorded and reproduced in such a recording apparatus as a VTR.
Now, in the above mentioned electronic endoscope, in order to obtain a color image of an object to be imaged, there is adopted in some cases a so-called frame sequential color imaging system wherein the outside diameter of the tip part is prevented as much as possible from being made larger by a solid state imaging device housed in the tip part of the insertable part.
In this frame sequential color imaging system, an object to be imaged is sequentially illuminated with an illuminating light of a different wavelength region, the sequentially illuminated object is sequentially imaged by a monochromatic imaging device and the image signals are synthesized to obtain a color image signal so that there may be obtained a color image of a higher resolution with an imaging device of a number of pixels smaller than in the case of a color imaging device using an optical color separating filter.
On the other hand, in the above mentioned frame sequential color imaging system, when the object moves, a color image having a color smear will be reproduced and therefore, in the case where the display picture is to be switched from a still picture to a moving picture, it will be necessary to detect and correct the color smear.
Also, in the case that the display picture is to be switched from a moving picture to a still picture, if the switching operation from the moving picture to the still picture is made at the time point when the positions of the object and imaging apparatus are moving relative to one another, a color smear will be generated in the still picture.
Therefore, in U.S. Pat. No. 4,901,143, there is disclosed a technique wherein the moved amount of an image signal is detected and is judged as to whether it is adapted to the memorizing conditions of the image signal for a still picture and, when it is judged to be adapted to the memorizing conditions, an actual image signal will be memorized to obtain a clear still picture.
However, with the recent development of video signal A/D converters, digital IC's and semiconductor memory devices, such various image processes as freezing images and dividing pictures have become compatible. As disclosed, for example, in U.S. Pat. No. 4712133, one display picture is divided into two display regions of a parent picture and son picture so as to generally visibly display information necessary for the diagnosis.
In such a case, a color smear for an image by the above mentioned frame sequential color imaging system will be corrected on the entire display picture. Therefore, heretofore, even in case one display picture is divided to display parent and son pictures so that one side may be a still picture and the other side may be a moving picture, the color smear has been corrected on both sides and, as a result, either the parent picture, which is a still picture, or the son picture has been deteriorated in the picture quality by the color smear correction and has likely become an unnatural picture.